- Restore any truncated space in the name prefix, before displaying
any error message.
- When trimming the name prefix from "special" characters (spaces, comma
and semicolon), so that e.g. "set ,; ,;FOO" displays all the variables
starting by "FOO", save also a pointer to the original name prefix, that
we will use for variables lookup as well.
This is done, because the SET command allows setting an environment variable
whose name actually contains these characters (e.g. "set ,; ,;FOO=42"),
however, by trimming the characters, doing "set ,; ,;FOO" would not allow
seeing such variables.
With the fix, it is now possible to show them.